"Biomass" is a principal source of cellulosic material and is one of the world's most abundant resources, being renewable via recurring plant growth. Hence, many efforts have been made to use it as a chemical feedstock, as in saccharification processes, for example. However, biomass and other cellulosic materials take so many diverse forms and are inherently so intractable as to make extreme demands upon design and control of any desired process.
Accordingly, it is convenient to subdivide chemical conversion of cellulosic material into successive stages, the first of which is usually called "pretreatment." The purposes of pretreatment include modification of physical or physical-chemical structure to render the cellulosic material more readily hydrolyzed or otherwise chemically converted subsequently.
Examples of known pretreatments of cellulosic material include application of strong acid, as by Classen in several patents, such as U.S. Pat. No. 695,795; alkali, as by Cross in U.S. Pat. No. 807,250; and weak acid, as by Corti in U.S. Pat. No. 826,299. Treatment by steam had (and has) numerous proponents, such as Tomlinson in many patents, including U.S. Pat. 1,032,443. Even more exotic pretreating agents have been employed, such as chlorine gas and sodium chloride (in electrolytic vessels), as by Gerull in U.S. Pat. No. 3,489,742; oxygen and alkali, as by Jividen et al. in U.S. Pat. No. 4,087,386; and metal chelates, as by Tsao in U.S. Pat. Nos. 4,174,976 and 4,265,675.
Cellulose pretreatments known in the prior art have the defect of either degrading its structure chemically to such an extent that the resulting increased type or variety of compositions becomes even less desirable and more difficult to control, or even introducing some additional undesirable compositions (or both). A successful pretreatment of cellulosic material ought to have the advantageous effects of modifying its composition and structure so as to improve its susceptibility to intended subsequent chemical conversion, and preferably to a range of chemical conversion processes or steps.
The present invention is designed to remedy the noted defects and to provide the suggested advantages, in a novel straightforward way without introducing additional difficulties into processing of biomass or other cellulosic materials.